The invention pertains to a device to adjust the rotary angle position of a camshaft relative to the crankshaft of an internal combustion engine according to the features the preamble of claim 1, and it is particularly advantageous for so-called vane-cell positioning devices.
A device of this type is already known from EP 0 818 610 A2. In this reference, there are five hydraulic working chambers inside an external rotor that are each subdivided into two pressure chambers by means of pivoting vanes. Between the bottom of the pivoting vanes and the base of the notch that receives the vane, there is a gap for vane pressure springs. The width and depth of this gap is determined by distance elements fastened at the bottom. The vane pressure springs effect a radial seating of the pivoting vanes against a cylindrical interior side of the working chambers. This is intended to effect a radial seal between the pressure chambers, which is required for a high functional reliability, efficiency and positioning speed of the vane-cell positioning device.
In DE 197 15 570 A1, a vane-cell positioning device is described with three hydraulic working chambers in the external rotor and with three pivoting vanes of the inner rotor. The pivoting vanes divide each of the working spaces into two pressure chambers. The radial seal between two pressure chambers is strived for by means of the thickness (=sealing length) of the pivoting vane and its centrifugal force, and the axial seal is strived for by means of spring-loaded sealing strips at the sides of the pivoting vane.
In EP 0 807 746 A1, a rotating vane positioning device is described in which an external rotor is provided with four hydraulic working chambers that are each divided by a vane from an internal rotor into two pressure chambers. The working chambers have a cylindrical internal contour and radial separating walls that extend to a hub of the internal rotor. Spring-loaded sealing strips serve as radial seals between the separating walls and the hub as well as between the vanes and the cylindrical internal contour. These sealing strips are intended to minimize the leakage between the pressure chambers.
Common to all three solutions is that the sealing elements are pushed by spring and/or centrifugal force against the sealing surfaces. Because of this, the danger exists that the sealing elements are lifted off of their sealing surfaces by the oil pressure in the pressure chambers, thus losing their sealing effect. This lowers the functional reliability, the effectiveness and the positioning speed of the device.
The object of this invention is to ensure the seating of the pivoting vanes against the interior perimeter of the external rotor in a device to adjust the rotary angle position of a camshaft with respect to a crankshaft of an internal combustion engine, in particular for a vane-cell positioning device according to the preamble of claim 1, within its entire rotational range.
According to the invention, this object is met by loading the bottoms of the pivoting vanes with oil pressure when the internal combustion engine is running. In this way, the pivoting vanes are hydraulically pressed against the interior perimeter of the external rotor. Since the pivoting vanes are also still forced outward by centrifugal force, depending on the rpm, the vane pressure springs can be eliminated, if necessary. Without vane pressure springs, the assembly of the vane-cell positioner becomes significantly simpler. Also, the influence of the contact pressure of the vane pressure springs on the function, and thus reliability of the vane-cell positioning device, is eliminated or reduced. The vane pressure springs are commonly just flat bent springs manufactured from flat spring band. The hydraulic loading of the bottoms of the pivoting vanes requires no additional space to work with.
It is advantageous to have the bottoms of the pivoting vanes in fluid communication with the pressure chambers or with their supply lines, in particular with annular spaces located in the interior of the rotor. In this way, the oil pressure in existence at the bottom of the pivoting vanes always matches that in the pressure chambers. This means that the higher the oil pressure in the pressure chambers and thus the tendency to lift off the pivoting vane, the larger is the pressing force and thus the seal between the pressure chambers. The result of a better internal oil seal is, mainly in the regulated position of the vane-cell positioning device, that less oil needs to be fed into the pressure chambers, which means an increase in the effectiveness and the positioning speed of the vane-cell positioning device.
It has been shown to be advantageous that the two working surfaces of the pivoting vane have preferably centered radial feed notches on them. Oil pressure passes through the feed notches from the pressure chambers into the gap and thus to the bottom of the pivoting vane. Since the oil pressure feed must occur from both pressure chambers, and thus a feed notch is required at both working surfaces of the pivoting vane, these are at the same time a leakage source. Therefore, their dimensions constitute a compromise between undesired throttling of the oil feed to the bottom of the pivoting vane and thus a delayed pressure build-up in the gap, and a desired throttling of flow to the other pressure chamber. The compromise solution is made easier in that the leakage flow into the neighboring pressure chamber is throttled twice as much as the fill flow into the gap.
In order to optimize this compromise, it is advantageous that in the installed position of the pivoting vanes, the feed notches extend from their bottoms to at least the area below the upper edges of the vane mounting notches. The required throttling can be attained by selecting the cross section of feed notches extending along the entire length of the pivoting vanes or by selecting the overhang between the vane mounting notch and the feed notches of the installed pivoting vanes extending up to just in front of their upper edges.
An advantageous development of the invention is that in a hub of the internal rotor and each vane mounting notch, an axial hole is provided that connects the two annular spaces to one another and intersects a radial hole that runs through the middle of each notch base. An axially shifting piston sealing slides inside the axial holes, which controls the radial holes and whose stroke is bounded on both sides by axial stops. In this way, the bottom of the pivoting vane is supplied with oil pressure alternatively from one of the two annular spaces through the axial and radial holes. The piston prevents a leakage flow from the pressurized annular space into the non-pressurized annular space. The two axial stops prevent the piston from falling out of the axial hole. They can be achieved by inserting drilled securing stoppers or discs on both sides, or by installing the latter into one side together with a diameter decrease at the opposite end of the axial hole.
It is also advantageous that the piston can be in the form of a circular cylinder or ball. The circular cylinder form ensures maximum leakage protection based on its large sealing length. The ball form offers a safer oil pressure supply to the bottom of the pivoting vane even if it is pressurized on both sides. The ball that then sits at the center position does not block the radial hole. When the cylinder shaped piston is in its center position in this mode of operation, which then blocks the oil feed to the bottom of the pivoting vane, this is not critical since in this case no drop in pressure and thus no oil leakage flow between the pressure chambers arises and thus the hydraulic radial pressing of the pivoting vane is not absolutely required.
The work to construct the oil pressure supply to the bottom of the pivoting vane is minimized by having the radial holes extend to a distributor notch that is made in a center hole of the internal rotor or on the external perimeter of a collar seated with a press fit in this center hole. In this way, one axial hole is sufficient to supply pressurized oil to all bottoms of the rotating vanes since the pressurized oil passes through the annular notch to all radial holes and thus to all of the bottoms.
An alternative solution to loading pressurized oil onto the bottoms of the pivoting vanes includes the gap having two partial spaces that are sealed from one another and that are in constant flow connection with different annular spaces. In this solution, the bottom of the pivoting vane is indeed only loaded on one half and eccentrically with oil pressure, but this eliminates any need to control the oil feed.
It is also advantageous that the pivoting vanes have a preferably round or square stem as seen in its cross sectional profile with a diameter or a thickness that is arranged perpendicular and centered at its bottom and it slides tightly within a radial guide hole in the hub of the internal rotor. In this way, sufficient sealing of the two partial gap spaces from one another is attained in a simple manner, so that despite no control of the pressurized oil feed, no short circuit flow between the two annular spaces results. If the stem has a larger length than the guide hole, it impacts the bottom before the bottom of the pivoting vane impacts the notch base of the vane mounting notch. The length difference between the stem and guide hole determines the height of the gap in this solution.
Another variation in the pressurization of the bottom of the pivoting vane includes the gap being connected to the two annular spaces by a feed opening for each of them made in the notch base, each of which is sealed off and controlled by a valve plate lying on the notch base and loaded by the vane pressure spring. This allows the oil pressure to pass into the gap in a simple manner and without leakage. The vane pressure springs and the valve plates are made of spring steel and can have an elastomeric coating to ensure the seal of the feed openings even with non-optimal surface quality of the notch base.
A particularly simple version of the pressurized oil feed system results by having the feed openings sealed off and controlled by the flat ends of the reverse-installed vane pressure springs. Here, the valve plate can be eliminated since its function is assumed by the correspondingly designed vane pressure spring.
A design which works selectively with or without vane pressure springs is characterized by a central spacer element whose purpose is to fix another valve plate that seals off and controls other feed openings. The other valve plate outside the area of the other feed openings and the central distance element have lateral play with respect to the vane mounting notch, as does a vane pressure spring, if necessary. The solution with the central spacer element is especially easy to assemble since the other valve plate whose length corresponds to the width of the pivoting vane must only be set into the vane mounting notch prior to its assembly. The lateral play between the vane mounting notch and the central spacer element or the valve plate and, if necessary, the vane pressure spring allows unthrottled loading of the bottom of the pivoting vane with oil pressure from the feed openings. The central spacer element, in comparison to the spacer elements located at the sides of the pivoting vane, offers the advantage of greater freedom to arrange the feed openings since the space required to cover them is greater by the width of the outer spacer elements.
Another advantageous development of the invention is characterized by the central spacer element being in direct contact with the notch base and in each of the two other partial spaces another U-shaped vane pressure spring is provided opening up toward the other feed openings, the spring shoulders of which lie against the other feed opening, sealing it off and controlling it. Here, the U-shaped vane pressure spring serves as a valve plate for the feed openings together with its spring force simultaneously acting as a closing force to cover the feed openings.
Other features of the invention can be found in the claims, the following description and the drawings, in which preferred embodiments of the invention are schematically represented.